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It would probably be difficult to find another animal on Earth that has adapted so perfectly to its environment. The Shark is a unique major predator Among current fauna, the Shark is a member of one of the oldest groups of animals to have outlived the dinosaurs. The oldest sharks appeared more than 420 million years ago. Today, more than 500 species of sharks are known. According to the International Union for Conservation of Nature (IUCN), about 30 % of Shark species are critically endangered, threatened or vulnerable.
Sharks are a large group of cartilaginous fish (Chondrichthyes), belonging to the same family group as Rays and Chimeras. Unlike bony fish, they do not have classic solid bones, but an internal bodily support by flexible cartilage and connective tissues.
Sharks primarily live in salt (sea-) water, although there are a few exceptions that occur in brackish waters at the mouths of rivers and penetrate their lower reaches, e.g. Bull Shark and River Shark. Sharks can be found in most seas and oceans on Earth.
Body Composition Sharks are very well adapted to movement in the water. They have a perfect hydrodynamic body shape, which allows them to move very quickly. They range in size from 6.7 inches for the Dwarf Lantern Shark (Etmopterus perryi), a deep-sea species of shark, up to the 40 ft-long giant Whale Shark (Rhincodon typus). Most sharks have 8 fins, but this is not always the rule. There are usually a pair of pectoral fins and a pair of abdominal fins. There can be 1 - 2 dorsal fins, 0 - 1 anal fins and a tail fin, which always has a more elongated upper segment.
Sharks do not have a gas bladder like other fish. This function is taken over by a huge liver (in large species, the liver can weigh up to 200 lb.), which is filled with a lot of light fat. The liver lifts the Shark as effectively as the gas bladder. In addition, it allows the Shark to change depth much faster than fish equipped with a bladder.
Sharks do not have gills like bony fish. The water flows in to the gills through the mouth and flows out through the gill slits. Some sharks can actively pump water into the gills with muscles. Many species do not have these muscles, and water flows around the gill arches only when the Shark moves forward: the faster it moves, the stronger the oxygenation. Therefore, a Shark that cannot swim suffocates, as oxygenated water stops flowing around the gills.
Did you know… sharks can not escape from a net, because they can't move backwards? That's why they can drown when becoming entangled in nets.
A Shark's skin is very rough and covered with enamel-like placoid scales, giving the Shark a kind of outer skeleton. Because the scales do not overlap, but touch each other, a number of tiny channels are created between them and the surface of the skin through which water can flow. The water thus easily flows around the Shark's body while swimming and there is no friction to slow it down.
Did you know… shark skin used to be used for sword hilts and for sanding wood?
The Shark’s jaw is unique in the animal world. Ancestors of the present-day Shark had the upper jaw firmly attached to the skull, and this determined the size of their prey. However, as the upper jaw evolved, it became detached from the cranial junction and became mobile. In this way, today's sharks can eat very large prey or pluck large pieces of meat from them. The jaw is controlled by very strong muscles. Researchers have measured a pressure of 3 tons per 2.5 inches in a 9-foot-long Shark (comparable to aprox. 500 lb. per 2.5 inches in a 150-lb human).
Shark teeth are very sharp. They have a triangular shape and are embedded in the jaw in solid connective tissue and arranged in several rows. However, only the first row is functional. Shark teeth have an unlimited ability to regenerate. After wear or damage, the teeth bend forward and fall out, and the next row will take over. The rate of tooth renewal can be 8-10 days, but also several months.
Speed Sharks usually swim in the ocean at 1.5 mph and wait for prey, then attack the prey at about 12 mph - the speed of a man running on ground. For comparison, an Olympic swimmer swims at a speed of 5 mph.
The Shortfin Mako Shark (Isurus oxyrinchus) is the speed champion of all sharks. Its top recorded speed is 34.8 mph. However, some sources say that it could reach speeds of up to 60 mph, because it catches Sailfish and Swordfish and these can reach speeds of up to 60 mph. The Mako is also the greatest jumper, as it can jump to a height of more than 20 ft.
Color Individual species of sharks have a nondescript color, ranging from gray to cream, brown, yellow, slate or blue, and often patterned with spots, streaks, marbling or protrusions.
Senses The Shark, as a major predator, has sensory organs at its disposal, some of which are completely unique to animals.
Did you know… intrauterine cannibalism is known in some Shark species, where the strongest embryos eat their weaker siblings?
Sharks are oviparous, ovovivipary or viviparous, and in the second group, intrauterine cannibalism can occur. The eggs of some species are over 8 inches in size. With the exception of the Bullhead Shark, egg cases are typically rectangular in shape with projections, called horns, at each corner. Depending on the species, egg cases may have one or more tendrils.
The lifespan of a Shark varies by species. Most of them live for 20 to 30 years. But there are exceptions, e.g. the Spiny Dogfish lives for about 100 years and the Greenland Shark can live up to 400 years.
Did you know… unlike many other sharks, the Great White Shark is not a major predator in all its natural habitats? This is because Killer Whales sometimes hunt it.
Shark Attacks on Humans Sharks have a very bad reputation and people fear shark attacks. In any case, the statistics show that you are more likely to be killed by lightning than by a shark attack. For example, in the coastal states of the USA, 1 970 people died from lightning strikes between 1959 and 2010 (i.e. 37.9 per year). During the same period, 26 people died after shark attacks (i.e. 0.5 per year).
Of the hundreds of known sharks, only about a dozen are dangerous, and only three species are responsible for most attacks on humans: the Great White Shark (Carcharodon carcharias), Tiger Shark (Galeocerdo cuvier), and Bull Shark (Carcharhinus leucas). Yet these attacks are not aimed at humans, but due to sharks’ confusion of humans with their natural prey.
Peter Benchley, author of the famous short story Jaws, said he regretted writing about sharks. "What I now know, which wasn't known when I wrote ‘Jaws’, is that there is no such thing as a rogue shark which develops a taste for human flesh," Benchley told the Animal Attack Files in 2000.
What are the main threats sharks are facing? All of them are caused by humans!
Commercial Fishing The biggest threat to sharks is overfishing. They are hunted for:
Climate Change and Habitat Degradation All sharks depend on healthy ecosystems and an abundance of food. Habitat degradation includes the effects of climate change, pollution and the destruction of areas such as mangroves and cliffs.
Before buying any product, make sure it does not contain any shark ingredients. By boycotting shark products, you will reduce the market demand, which will cause companies to stop killing sharks to produce such goods. What else can be done?
Prohibit the removal of fins at sea Finning is a barbaric practice of cutting the fins of a live shark and throwing the rest of the body into the sea. Laws need to be changed, so that these cruel hunting practices are not possible and are punishable by Law.
Fight for more Sustainable Fishing Many sharks get stuck in nets as bycatch. It is necessary to review laws and to upgrade fishing vessel equipment to end deadly fishing.
More rigorous Shark Protection New laws need to be enforced to protect endangered Shark species. Along with the laws, it is necessary to control fishing vessels and monitor fishermen's behavior.
Monitoring of Sharks Satellite tracking of sharks serves to better understand shark migratory routes and their behavior in the open seas. It can also serve as a protection against the attacks on humans by the most dangerous sharks, without having to kill them.
Cleansing the Oceans An increasing volume of trash is entering the oceans and this trend must be stopped. Tougher waste management policies are necessary in all countries, as well as active support for ocean cleansing projects.
Education As it is very difficult to push for changes in shark protection, it is necessary to ensure better awareness of this issue in the first place. Many people still think that there is an infinite number of sharks and so there is no need to worry about their future.
Everyone can get involved. How can YOU help?
Do not use Shark Products Shark Fin Soup is a great gourmet experience, but remember that every serving means a dead shark, having cruelly had its fins removed while still alive, for your plate! However, there are also other shark parts used.
Reduce your Consumption of Seafood Commercial fishing significantly reduces the population of food resources and sharks also die as collateral damage of commercial fishing. By simply reducing your own consumption of seafood, you can reduce the number of sharks killed each year.
Recycle Waste is a threat to the entire marine ecosystem, and the Shark is no exception. Trash (e.g. plastic) is consumed by the marine species which make up sharks’ food. As a result, this trash also reaches sharks, causing them illness and subsequent death. With each bit of recycled waste, this risk is reduced.
Spread Awareness Social networks are a powerful tool and you can spread information about the situation of the Shark to your friends and acquaintances.